Re: [Qemu-devel] [PATCH v4 2/8] acpi: add vmcoreinfo device

[Marc-André Lureau]

Hi

On Fri, Jul 14, 2017 at 10:17 PM, Michael S. Tsirkin <address@hidden> wrote:
> On Fri, Jul 14, 2017 at 10:04:31PM +0200, Laszlo Ersek wrote:
>> > It worries me that the format of this seems completely undefined
>> > except in the patchset cover letter.
>> > I don't think we should merge this before it is.
>>
>> I'm not sure what you mean, this patch adds "docs/specs/vmcoreinfo.txt".
>> That file is the first level contract between the guest firmware
>> (generally, via the linker/loader), the guest kernel driver
>> (specifically), and QEMU (also specifically).
>>
>> The second level contract is the guest kernel's vmcoreinfo ELF note
>> (which is pointed-to by the first level contract). The layout of that is
>> specified elsewhere indeed (I don't think it belongs here).
>>
>> We've taken care not to trust anything coming from the guest kernel.
>>
>> Can you clarify please?
>>
>> Thanks
>> Laszlo
>
> All there is is this:
>
> +Version 0 content:
> +
> + uint64 paddr:
> +  Physical address of the Linux vmcoreinfo ELF note.
> + uint32 size:
> +  Size of the vmcoreinfo ELF note.
>
> It isn't defined here what is the Linux vmcoreinfo ELF note.
> You want a bit more info so people trying to use it know where to start
> and what they can get out of it.

QEMU is not responsible for the content of the ELF note. All there is afaik is:

https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-kernel-vmcoreinfo

The rest you need to dig in the kernel code and git history I think.

-- 
Marc-André Lureau